The present invention relates to an electrochemical analysis element that facilitates rapid and accurate quantitation of a specific component contained in a biological sample such as blood, sweat or the like, or food sample such as food raw material or food product from food industries.
The biosensor disclosed in the Japanese Laid-Open Patent Publication No Hei 3-202764 is a known example of electrochemical analysis element that facilitates simplified quantitation of a specific component, that is, a substrate contained in a biological or food sample without necessitating dilution and subsequent stirring of a sample solution. The biosensor disclosed in this reference is produced by first forming an electrode system on an insulating base plate using screen printing method or the like and subsequently forming a reaction layer containing an oxidoreductase and an electron acceptor on the formed electrode system.
This biosensor quantitates the substrate concentration in a sample by the following procedure.
First, dropping a sample solution on the reaction layer of the biosensor dissolves the reaction layer in the sample solution, which promotes enzyme reaction between the substrate in the sample solution and the oxidoreductase in the reaction layer. Upon enzyme reaction, the electron acceptor in the reaction layer is reduced. A voltage is applied across the electrodes of the sensor after a predetermined time to electrochemically oxidize the reduced electron acceptor. The substrate concentration in the sample is quantitated based on the oxidation current value across the electrodes.
The prior art electrochemical analysis element can readily determine the substrate concentration in a sample of several xcexcl or more. However, such element has a drawback that it sometimes meets difficulties in making reliable measurement if the sample is very small in amount under several xcexcl.
The object of the present invention is therefore to provide an electrochemical analysis element that enables reliable measurement of a trace amount of sample.
The electrochemical analysis element in accordance with the present invention comprises a sensor body having a hollow space which space is open at its both ends, an electrode system having a working electrode and a counter electrode and a reagent segment containing an enzyme, wherein the electrode system and the reagent segment are disposed on an inner wall of the hollow space.
In a preferred mode of the present invention, the working electrode is positioned to oppose to the counter electrode on the inner wall of the hollow space.
In another preferred mode of the present invention, the reagent segment further comprises an electron acceptor.
In still another preferred mode of the present invention, the reagent segment is disposed on the working electrode.
When the sample is whole blood, an arrangement of a filter on at least one open end of the hollow space helps to filter red blood cells during passage of the whole blood through the filter. This eliminates inconveniences due to arrival and interference of red blood cells at the reagent segment.
Closure of both open ends of the hollow space with a resin film or aluminum laminate film can enhance reliable preservation of the reagents in the reagent segment.
According to the present invention, a provision of a reagent segment containing glucose oxidase yields an electrochemical analysis element that can quantitate glucose in body fluids. A provision of a reagent segment containing cholesterol oxidase in combination with cholesterol esterase yields another electrochemical analysis element that can quantitate cholesterol in body fluids.
While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings.